Methods of Controlling Growth of Steelhead

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Abstract
Steelhead (Salmo gairdneri) held at 15°C and fully fed from demand feeders grow larger than desired by the time of their normal release into streams. The effect of limited feed intake on growth, body composition, and potential for migration to the sea was investigated. Dilution of feed by 10-40% with sodium bentonite was not effective in reducing growth; the fish used the nutrients more efficiently and their growth was nearly equal to that of controls. Hand feeding of a decreased ration reduced growth rate, but about a 50% reduction in feed was required to effect the desired reduction in growth rate. Fish were able to compensate for fasting periods of short duration and significant growth reduction did not occur until the fasting periods were 4 d or longer. Alternate feeding and fasting periods of equal lengths produced the desired growth rate reduction. Estimated potential for emigration by these anadromous fish was not reduced by fasting periods as long as 28 d.